Responses of the intestine of the giant African snail (Achatina fulica) to acetylcholine in Meng's solution with low sodium, potassium and calcium ions.

Decreasing the concentration of sodium in Meng's solution produced a non-parallel shift of the dose-response of acetylcholine on the intestine of the Giant African Snail Achatina fulica. This decrease in sodium decreases the sensitivity of the tissue to acetylcholine and sensitivity was not restored with several washings. The response to decrease calcium is very similar to that of sodium. In the case of potassium however 10% K+ produced less depression in sensitivity than 25% which even caused less depression of sensitivity compared with 50% potassium. The results show an abundance of spare receptors.